The most general and widely used method for obtaining substituted guanidines (B) is from corresponding substituted (aminomethylene) ammonium halides (A) with one mole of a primary amine: ##STR1## wherein X is a monovalent substituent selected from the following radicals: --P(O)Cl.sub.2 ; --PCl.sub.4 ; --S(O)Cl; --S(O)--R and --C(O)--R'; W is oxygen or sulfur; Y is chlorine or bromine; R is a monovalent substituent selected from the group consisting of hydrogen, alkyl, aryl, aralkyl, alkaryl, cycloalkyl, alkenyl, cycloalkenyl and heterocyclic radical; R' is a monovalent organic radical independently selected from the group consisting of alkyl, aryl, aralkyl, alkaryl, cycloalkyl, alkenyl, cycloalkenyl and heterocyclic radical.
The yields are, however, only mediocre and vary in general from 40 to 70% of the theory, as documented in (a) Journal of Organic Chemistry, Vol. 32, pp. 2511-2516 (1967); (b) Chemische Berichte, Vol. 94, pp. 2278-2295 (1961); and in the book (c) of P. A. S. Smith, Open-chain Nitrogen Compounds, Vol. 1, pp. 281-282, (1965), W. A. Benjamin, Inc. New York.
Compounds of general formula (A) are available by the reaction of substituted ureas with one of the following reactants: P(O)Cl.sub.3, PCl.sub.5, SOCl.sub.2, RS(O)Cl and RC(O)Y: ##STR2## wherein X,Y,W,R and R' are as defined above. In contrast to reaction (I), the yields in reaction II are generally high, varying from 80 to 99%, as indicated in reference (b) quoted above.